1. Field of the Invention
The present invention relates to a block copolymer of polysiloxane blocks and polyurea blocks.
2. Background of the Invention
Aminoalkyl end blocked polysiloxanes show promise as the precursors to prepare many types of siloxane-organic block copolymers. However, the aminoalkyldimethylsiloxy endblocking units which are needed to make these precursors are either not readily available, or are too expensive because they require a capital investment which inhibits commercialization of the products using them. The expense is reduced if the precursors are of a higher molecular weight such as those which have greater than 100 units per molecule, because the amount of endblocking unit required for such polymers is lower as the molecular weight of the polysiloxane increases. But to make high modulus, high strength materials, lower molecular weight precursors are required, such as those having less than 50 siloxane units per molecule. Therefore, other ways of connecting the siloxane block to the organic block were investigated.
Silicone aryloxy materials have been reported to have reasonable hydrolytic stability and siloxane polysulfone block copolymers in which the siloxane was bonded to the polysulfone by an aryloxy linkage was reported by R. D. Lundberg, in "Handbook of Thermoplastic Elastomers", Walker, B. Med. Van Nostrand Reinhold Company, N.Y., p. 270 (1979), to have better hydrolytic stability than polyurethanes.
The search for aryloxy silicone precursors for making polysiloxane-polyurea block copolymers lead the present inventors to select aminoaryloxy functional siloxanes. However, these materials are unavailable and the particular precursors need to be prepared. One method of preparing aminoaryloxy silanes or siloxanes is reported by Patterson et al, in J. of Polymer Science, Part A-1, 1089-1110(1969). Patterson et al teach preparing the aminoaryloxy silanes or siloxanes by the following reaction ##STR1## in which m has a value of 1, 2, or 3. Patterson et al teach reacting these aminoaryloxy silanes and siloxanes with epoxy functional siloxanes to make thermoset epoxy resins with high dielectric constants and good toughness at low temperatures.
Butler et al in the First Annual Summary Report, Thermally Resistant PolYmers For Fuel Tank Sealants, Contract No NAS8-21401 DCN-1-8-54-10236(1F) and S1(1F), (1969), at pages 9 and 35, teach aminophenoxy siloxanes by the following reaction ##STR2## in which y is 1 or 2. Butler et al react the aminophenoxy siloxanes with phosgene to make the isocyanate derivative.